I might suggest trying to use a different DNS server. It's been known that Comcast has filtered e-mails and such from SE, and if they saw a lot of traffic all going to one specific SE website they may have filtered it as well.

Google provides free DNS servers:
8.8.8.8
8.8.4.4

Just change the settings in your Network Connections > TCP/IP (IPv4) settings for your DNS server.